The CBSD Macromolecular X-ray Diffraction Core (MXDC) provides support, expertise, and infrastructure to CBSD COBRE Investigators and University of Montana laboratories that use X-ray crystallography as a tool to determine the three-dimensional structures of small molecules and biological macromolecules, and seek to express and purify proteins and RNA for biochemical, biophysical and structural studies. The MXDC possesses the infrastructure and expertise to provide comprehensive user access to shared major instrumentation and research training for expression of recombinant proteins in bacteria and insect cells, robot- assisted crystallization of macromolecules, evaluation of crystallization experiments, and measurement of diffraction data from crystals of both small and macromolecules and determination of their three-dimensional structures at atomic or near-atomic resolution. The facility houses a Rigaku 007HF X-ray generator and R-axis image plate detector for macromolecular crystallography and a Bruker D8 Venture fixed Chi dual source diffractometer for small molecule applications. Both instruments feature Oxford liquid-nitrogen crystal cryo- cooling-systems. The MXDC routinely measures X-ray diffraction data from crystals at synchrotron sources at single and multiple wavelengths for structure determination by molecular replacement, heavy atom, and anomalous dispersion phasing. Computational resources of the MXDC are also available for X-ray data processing, structure determination, refinement, and visualization for both small-molecule and macromolecular structure determination. The MXDC encourages a collaborative model, in which faculty, students and staff conduct projects with assistance and training from Core personnel. The MXDC is a resource for training, education, consultation and collaboration in protein expression/purification and both small molecule and macromolecular X-ray crystallographic techniques. The specific aims of this component of the Phase II CBSD COBRE are: 1, to oversee and maintain a productive collaborative facility by adopting procedures for project planning, an appropriate fee structure and project reporting mechanism, and both short-term and strategic planning with the guidance of an Advisory Committee; 2, to maintain and enhance gene-to-structure and small molecule structure determination services by implementing state-of-the-art technologies; 3, to pursue research collaborations with CBSD COBRE investigators in aspects of their projects that involve areas of MXDC expertise; and 4, to provide training in practical application of techniques in protein expression, purification, crystallization, and X-ray structure determination (macro and small-molecule) for CBSD investigators and UM faculty through direct collaborations, workshops, lectures, the MXDC website and the MDXC Core Fellowship Program. 1